58 research outputs found
Polarized thermal emission by thin metal wires
We report new measurements of the linear polarization of thermal radiation
emitted by incandescent thin tungsten wires, with thicknesses ranging from five
to hundred microns. Our data show very good agreement with theoretical
predictions, based on Drude-type fits to measured optical properties of
tungsten.Comment: 12 pages, 4 encapsulated figures. This new version matches the one
published in New. J. Phys.. Improved presentation, more references added, and
one new figure include
Coherent coupling between multiple ferrimagnetic spheres and a microwave cavity in the quantum-limit
The spin resonance of electrons can be coupled to a microwave cavity mode to
obtain a photon-magnon hybrid system. These quantum systems are widely studied
for both fundamental physics and technological quantum applications. In this
article, the behavior of a large number of ferrimagnetic spheres coupled to a
single cavity is put under test. We use second-quantization modeling of
harmonic oscillators to theoretically describe our experimental setup and
understand the influence of several parameters. The magnon-polariton dispersion
relation is used to characterize the system, with a particular focus on the
vacuum Rabi mode splitting due to multiple spheres. We combine the results
obtained with simple hybrid systems to analyze the behavior of a more complex
one, and show that it can be devised in such a way to minimize the degrees of
freedom needed to completely describe it. By studying single-sphere coupling
two possible size-effects related to the sample diameter have been identified,
while multiple-spheres configurations reveal how to upscale the system. This
characterization is useful for the implementation of an
axion-to-electromagnetic field transducer in a ferromagnetic haloscope for dark
matter searches. Our dedicated setup, consisting in ten 2 mm-diameter YIG
spheres coupled to a copper microwave cavity, is used for this aim and studied
at mK temperatures. Moreover, we show that novel applications of
optimally-controlled hybrid systems can be foreseen for setups embedding a
large number of samples.Comment: 12 pages, 8 figure
The QUAX proposal: a search of galactic axion with magnetic materials
Aim of the QUAX (QUaerere AXion) proposal is to exploit the interaction of
cosmological axions with the spin of electrons in a magnetized sample. Their
effect is equivalent to the application of an oscillating rf field with
frequency and amplitude which are fixed by axion mass and coupling constant,
respectively. The rf receiver module of the QUAX detector consists of
magnetized samples with the Larmor resonance frequency tuned to the axion mass
by a polarizing static magnetic field. The interaction of electrons with the
axion-equivalent rf field produces oscillations in the total magnetization of
the samples. To amplify such a tiny field, a pump field at the same frequency
is applied in a direction orthogonal to the polarizing field. The induced
oscillatory magnetization along the polarizing field is measured by a SQUID
amplifier operated at its quantum noise level.Comment: 5 pages, Contribution for the proceedings of the TAUP2015,
International Conference on Topics in Astroparticle and Underground Physics,
7-11 September 2015, Torino, Ital
Resonance frequency shift in a cavity with a thin conducting film near a conducting wall
We show that a very thin conducting film (whose thickness can be much smaller than the skin depth), placed nearby a wall of an electromagnetic cavity, can produce the same shift of the resonance frequency as a bulk conducting slab, provided the displacement of the film from the wall is much bigger than the skin depth. We derive a simple analytical formula for the frequency shift and compare it with exact numerical calculations and experimental data
The measurement of a single-mode thermal field with a microwave cavity parametric amplifier
In this paper, we present the experimental study of a single-mode thermal field carried out using a microwave parametric amplifier tuned at 1.5 GHz and working at room temperature. The parametric amplifier is based on a variable capacitance diode placed inside a microwave resonant cavity. The measured distribution of the thermal photons inside the resonator follows the expected Bose–Einstein distribution probability
Cascade Superfluorescence in Er:YLF
We report the analysis of paired photon pulses arising from two cascading
transitions in continuously pumped Erbium-doped YLiF 1% and 0.01% crystals
at 1.6 K. The dependence of the pulse peak intensity on the squared number of
involved Erbium ions, between 10 and 10, definitely identifies
the cooperative nature of the two pulsed emissions, that are generated by the
subsequent, spontaneous formation of coherent states. The observed fluctuations
of the time interval between the paired pulses and, most importantly, its
correlation with the second pulse duration, demonstrate that the Erbium ions
coherence is indeed seeded by vacuum fluctuations
Experimental perspectives in (low-energy) photon-photon scattering
The possibility of photon-photon scattering is a striking difference between classical and quantum electrodynamics. This genuinely quantum feature is made possible by the fluctuations of charged fields, and it makes quantum vacuum a nonlinear optical medium. Photon-photon scattering is thus a delicate probe into the structure of quantum electrodynamics and any departure from the expected behavior would be a powerful signal of "new physics". To date this process has never been observed – except as a radiative correction to other processes – and several experiments are trying to detect it at very low energy, in the scattering of real photons in powerful light beams off the virtual photons of intense magnetic fields. Here we briefly review the experimental state-of-the-art, with special emphasis on the PVLAS experiment, and we describe a new proposal to observe photon-photon scattering in the range 1 – 2 MeV
- …